Method for recovering oil



Jan. 5, 1965 w. H. THEssEN ETAL 3,164,207

METHOD FOR RECOVERING OIL 2 Sheets-Sheet l Filed Jan. 17. 1961 INVENTOR)` nejghessen f om pry JA/M/*ahm Jam 5, 1965 w. H. THESsEN ETAL 3,164,207

METHOD FCR REcovERING OIL 2 Sheets-Sheet 2 Filed Jan. 17, 1961 INVENTORS ATTORNEYS United States jatent 3,164,207 METHB EUR RECOVEPIING OIL Wayne H. Thessen, 129 Totten Holiow, Bradford, Pa.,

and William I. Spry, 17537 Daleview Ave., Lakewood 7, @ino Filed lian. I7, 1961, Ser. No. 83,348 2 Claims. (Cl. 16o- 39) The present invention is a continuation-impart of our co-pending application Ser. No. 835,467 filed August 24, 1959, now abandoned.

The present invention relates to a new and novel method for recovering valuable liuids from fluid-bearing strata. While the invention is applicable to the heating of subterranean strata bearing various types of uids therein, the invention is especially adapted for thevrernoval of oil from oil deposits.

It is well recognized in the art that in a majority of oil deposits now existing, only a minor portion of the oil in the deposits can be removed in a commercially profitable manner or in fact most of the oil in many deposits can not be removed at all.

After an oil deposit has passed through the stages of being a gusher wherein the natural gas pressure forces the oil out and then subsequently the oil is pumped out by conventional pump means, the oil in the huid-bearing strata becomes excessively viscous and waxy such that it can not be pumped by conventional means. As a result of this common condition, many methods have been attempted for recovering the oil in such deposits. Some of these methods are primarily concerned with 'providing a source of heat which will sufficiently raise the temperature of the oil such that it can be successfully forced out of the strata within which it is lodged. It is of course evident that the successful application of sumcient heat to the relatively large area involved is a major problem, compounded largely by the fact that only limited access to the strata is available through relatively small bore holes.

While it has long been recognized that the successful application of heat to the strata will actually cause the oil to become less viscous and thereby more readily removable, the methods and apparatus employed in the prior art have provided only very limited success due to the fact that these arrangements have not successfully solved the problem of obtaining a sufficient heat transfer from an economical source of heat.

Prior art methods have employed chemical heating means or electrical heaters suspended within the bore holes adjacent the fluid-bearing strata and the passage of electric current through the formation by the use of electrodes in a plurality of adjacent wells has been attempted. Additionally, gases have been pumped down into a Well from the surface to` a point adjacent the fluidbearing strata, and the oil itself has even been ignited to produce gases which would generate pressure to force the oil up out of the well while heating the viscous oil in the deposit. Each of these various methods and the apparatus employed therewith possesses certain inherent disadvantages and accordingly, they have met with konly very limited success such that the majority of the oil in known deposits throughout the world is at present unrecoverable.

Prior art systems and methods for recovering oil have failed for two primary reasons. Firstly, the prior art arrangements have encountered major difficulties in supplying an adequate source of heat within the bore hole itself over extended periods of time. When utilizing conventional heat sources such as electrical heaters or some sort of chemical heating means, it is, of course, necessary to transmit a supply of energy from the surface at all times downwardly into the bore hole. Accordingly, such prior art arrangements haveencountered transmission problems in attempting to vefficiently transmit a continuous source of energy to the heating means itself. Even where this transmission problem has been solved to a certain extent, difficulties have arisen in accurately controlling the amount of heat supplied within the bore hole. In this connection, it must be recognized that the amount of heat applied within the bore hole can not be increased arbitrarily, but must be maintained within certain limits in order to avoid charring of thecrude oil. If such charring does occur, the removal of the oil may become :more diticult than ever if not impossible.

A secondv major failing of prior art` apparatusand methods forA removing oilr has been in the lack of an efficient means for effectively transferring the heat from a heat source within the bore hole to the oil-bearing strata itself. Such heat sources as heretofore employed for these purposes are for all intents and purposes from a thermo-dynamic standpoint a point Isource of heat since the actual dimension of the heating source itself is practically negligible as compared to the extent of the bore hole which may be many hundreds of feet long. .It will be recognized that it is completely impractical to provide a source of heat whichis itself fully coextensive with the bore hole. Accordingly, the decay in temperature from such point sources of heat is very rapid, and since the oil-bearingV strataV has a thermal conductivity similar to the rock above andbelow it, the isotherms or regions of even temperature approximate concentric spheres from the source of heat.

With such a point source of heat, the temperature decay within the heated mass varies essentially'as the inverse of theradius squared. Accordingly, prior art arrangements have failed to effectively heat a large volume of the oil-bearing strata which is absolutely essential to obtain eicient recovery of the oiltherein.

The two major disadvantages of the prior ant referred to above have been overcome in the present invention by the provision of a unique and novel arrangement. The present invention contemplates as a source of heat a nuclear reactor which does overcome certain of the disadvantages encountered with prior art arrangements. It

ris pointed out that various types of nuclear reactors may be employed in the present invention and the particular nuclear reactor disclosed herein is'for the purpose of illustration only. In addition, other sources of heat may be employed such as electrical heating means or chemical heating sources, but it is considered that .the nuclear reactor heating source is far `superior and presents many advantages not obtained with any other type of heating means.

The nuclear reactor heating means is adapted to generate heat over extended periods of time thereby permitting the heat to effectively permeate the oil-bearing strata, and the heat generated'by the reactor may be very accurately controlled. In this manner, the generation of any excessive heat may be readily avoided, and the danger of charring the crude oil is eliminated.

In addition, it is not necessary to provide any additional source of heating energy from the surface once the reactor is inserted in operative position, but it is only necessary to provide a small amount of power preferably in the form of electrical energy for controlling `the opera- Y tion of the reactor. Accordingly, the transmission prob- Y lems of prior art systems is eliminated.

The present invention also incorporates a unique con;V

bore hole. A body of heat-conducting fluid is then disposed in the bore hole between the heat exchanger and the wall of the bore hole. The bottom of the bore hole is plugged such that the body of heat conducting fluid does not escape therefrom, and means is provided for controlling the level of this body of fluid such that it lls that portion of the bore hole extending through the oilbearing strata whereby the column of heat-conducting fluid is in intimate contact with the wall of the bore hole throughout the extent of the oil-bearing strata. ln certain instances, it may be preferable to provide a column of heat-conducting tluid which extends both above and below the oil-bearing strata as will hereinafter appear.

Circulating pump means is provided for circulating thi body of heat-conducting fluid around the heat exchanger and along the walls of the bore hole. This continuous movement of the heat-conducting fluid provides a very etlicient heat transfer from the heat exchanger to the relatively large expanse of the wall of the bore hole, and furthermore ensures that such heat is uniformly distributed along the wall of the bore hole. In this manner, it is possible to provide a primary source of heat which is of a relatively small dimension such as a nuclear reactor, and this primary source of heat is transferred through an elongated column of heat conducting Huid to the wall of the bore hole throughout the extent of the oil-bearing strata. Accordingly, the present invention effectively provides a line source of heat rather than a point source of heat, the line source of heat, of course, being considered the column of heat conducting fluid which actually transfers heat to the source of the bore hole. This line source of heat is greatly superior to the prior art point source of heat since the decay of temperature in a heated mass from a line source of heat is slow and essentially logarithmic. In this manner a much more eiicient heating of the oil-bearing strata is obtained.

Means is provided extending from the surface down within the bore hole to the reactor for controlling the output of the reactor such that the heating of the oilbearing strata may be eiectively controlled from the surface. Means is also provided in the form of `a conduit extending from the surface to a point below the reactor for providing iluid under pressure to assist in the removal of the heated oil by generating a pressure which radiates outwardly from the central bore hole to force the heated oil upwardly Ithrough the adjacent surrounding bore holes. This last-mentioned means may be also employed for controlling the level of the heat-conducting fluid within the bore hole to ensure that the column of such fluid extends along the wall of the bore hole throughout the vertical extent of the fluid-bearing strata.

A further conduit means is provided which extends from the surface to a point below the reactor for venting gas which may accumulate in the bore hole beneath the reactor. Such gas as may accumulate should be removed since the thermal ethciency of the heat transfer from the source of heat to the wall of the bore will be impaired by such accumulation of gases.

An object of the present invention is to provide a new and novel method and apparatus for recovering oil from a subterranean deposit wherein the oil cannot be recovered by conventional pumping methods.

Another object is to heat the oil within the desired fluid-bearing strata and to provide a very eicient and effective means for transferring the heat from a heater to the strata to thereby reduce the viscosity of the oil in the strata.

Yet another object of the invention is to provide effectively a line source of heat extending vertically within a Huid bearing strata to thereby provide a most effective source of heat for the strata.

A further object of the invention is to provide a remote control means for accurately governing the heat generated by the apparatus of the present invention.

Still another object of the invention is to provide a method for recovering oil which is simple and may be carried out even by relatively inexperienced personnel.

A still further object of the invention is to provide apparatus for recovering oil which is simple and inexpensive in construction, and yet which is eicient and reliable in operation.

Other obiects and many attendant advantages of the invention will become more apparent when considered in connection with the speciiication and accompanying drawings, wherein:

FG. l is a plan view of one possible array of oil wells according to the present invention;

FlG. 2 is a brokennway sectional perspective view of the oii well array shown in FIG. l;

FEG. 3 is a longitudinal section of a bore hole having the apparatus inserted in operative position therein;

4 is an enlarged sectional view of the reactor mechanism of the present invention;

FIG. 5 is a sectional view taken along line 5 5 of FG. 3 looking in the direction of the arrows; and

FlG. 6 is a broken away sectional view illustrating an arrangement wherein the column of heat-conducting uid within the bore hole extends both above or below the level of the fluid-bearing strata.

Referring now to the drawings wherein like reference characters designate corresponding parts throughout the several views, there is shown in FIG. 1 a central bore hole llt) which is surrounded by four substantially equally spaced bore holes 11, the bore holes 1) and it representing a typical tive-spot oil well layout. The central bore hole 10 has been shown as being slightly larger, although it should be understood that each of the bore holes may be of the same size it desired. For the purpose of illustration of the present invention, it will be assumed that the heating mechanism is inserted in the central bore hole l@ and that the heated oil is recovered from the surrounding boreholes 11.

As seen in FIG. 2, each of the ve bore holes extends downwardly into a huid-bearing strata indicated by dimension A which is shown as lying between two layers of cap rock thereby representing a typical natural condition. It will be noted that the upper ends of each of bore holes 11 are capped with caps 12, and conduits i3 are connected in communication with the interior of each of these bore holes, the conduits extending to a common reservoir 15' which may be employed for collecting the oil which is recovered through each of the bore holes l. A pump 16 such as commonly used in oil recovery is connected in each of conduits )i3 for assisting in drawing the oil out of the bore holes.

A control panel indicated generally by reference numeral 2@ is provided with various gauges and switches for controlling the operation of the apparatus which will be explained more fully hereinafter, and an electric cable 21 being connected to the control panel extending downwardly to connect with the various components of the apparatus within the bore hole.

A casing head 25 is provided at the upper end of the bore hole, the casing head being preferably sealed with respect to the opening at the surface and serving additionally to support the apparatus suspended within the bore hole itself. A gas vent conduit 26 extends upwardly above the casing head and has a manually operated onot valve connected therein for selectively opening or closing the conduit as desired.

A fluid pressure conduit Si? also projects upwardly above the casing head and is connected with a pump 31 which is selectively actuated as hereinafter described to supply fluid under pressure downwardly below the reactor.

The apparatus suspended Within the central bore hole l@ is illustrated somewhat schematically in FIG. 2, and it is apparent that the interrelationship of the various bore holes is such that when the heating means within bore hole It@ is energized, the heat created thereby Will radiate outwardly through the fluid-bearing strata to points adjacent the other bore holes 11 thereby permitting the oil to become less Viscous and to flow readily into bore holes 11 to be subsequently recovered therefrom. This action may be most clearly understood from an inspection of FIG. 1, wherein the various concentric circles as shown in phantom lines indicate the temperature gradient drop from central bore hole lil, it being apparent that the highest temperatures will exist at the innermost circles and that the temperatures will successively become less moving away from the central bore hole. The heat will radiate outwardly to the extent indicated with the passage of time. The heating of crude oil usually causes the generation of gas which assists in forcing more oil to flow into the bore holes 11.

Referring now to FIG. 3 of the drawings, a central supporting hollow cylindrical member d@ is suspended through a central aperture in casing head and is supported thereby. Fluid pressure conduit 3l? extends downwardly through the hollow interior of member 4t?, and the gas vent conduit 26 also extends downwardly through a suitable opening provided in the casing head. Electric cable 21 similarly passes downwardly through an opening in the casing head.

The wall is sealed off at the upper portion thereof by providing a conventional packer 41 which engages the outer wall of the bore hole and is sealed with respect thereto. Cylindrical member 4?, gas vent conduit 25 and electric cable 21 each extend downwardly through suitable openings provided in the packer and are sealed with respect thereto.

Connected to the lower end of cylindrical member iti and supported thereby is an elongated hollow housing d5, housing 45 being divided into three chambers 46, 47 and 43. A junction box St! is mounted on top of housing 45 and the lower end of electric cable 21 is connected thereto. The various electrically driven components hereinafter described are each connected to the junction box in a well-known manner, these individual connections not being shown for the purpose of simplicity, it being understood that the pigtails `connected to the various components as indicated are in turn connected to the junction box in a conventional manner. in the lowermost chamber 48 of housing i5 is mounted a nuclear reactor for producing the heat. While it is evident that this reactor may assume any formation, the reactor must be of such construction that it can be inserted in oil well bore holes that can be drilled with presently known methods, preferably of the size presently in existence in oil fields such that these previously drilled bore holes may be utilized. A reactor which is particularly suitable for the purposes of thepresent invention and which is disclosed herein is of the so-called TRIGA type. This type of reactor is relatively simple and efficient in operation, and is suitable for the present purposes. lt should be understood that other types of reactors may be employed, the water cooled reactor as disclosed herein being an example. The reactor of the present invention is disclosed in more detail in FIGS. 4 and 5.

Referring now to FIG. 4, the reactor itself comprises an outer cylindrical shield or reector which preferably comprises graphite or other suitable substance such as beryllium or compounds thereof, the graphite material or the like being enclosed in a suitable container such as a welded metal can 56. A bottom grid plate 6@ closes the lower end of the cylinder and the top grid plate 61 closes the top end of the cylinder. Plates 60 and 61 are provided with a plurality of openings 66) and 61' respectively which receive the lower and upper ends of the fuel elements mounted within the reactor. The core consists of a cylindrical array of fuel elements, these elements being indicated by reference numerals 65. A relatively large number of fuel elements may' be provided in accordance with the desired output of the reactor, a typical example consisting of about fuel eletoY to independently shut down the reactor.

ments interspersed with aboutAZO graphite dummy elements.

As mentioned previously, the upper and lower ends of the fuel and dummy elements are supported by the grid plates, the elements being provided with reduced end portions which t within the openings provided in the grid plates. The fuel'elements themselves form no partof the present invention, but are described herein in order to clarify the disclosure. Each fuel element Vconsists of a central cylindrical portion composed of zirconium hydride mixed with 8 to 20 percent by weight of enriched uranium. Above and below this Vcentral cylindrical portion are considerably shorter cylindrical sections of graphite. Interposed between the central fuel section and the graphite sections are discs containing an appropriate amount of samarium so that the excess reactivity necessary to overcome samarium ybuild-upis minimized. Aluminum and fixtures are secured to each end ofthe elements for mounting them in operative position.

Suitable control rods are provided for moderating the reactor, the control rods being shown as three in number and being indicated by reference numerals 70, 71 and 725.l Each of these control rods is formed of a suitable moderating material such as boron carbide. Each control rod may be provided with suflicient reactivity worth Openings are provided lin the upper grid plate aligned with each of the control rods, and three corresponding guide tubes 71'v and 72 are 'supported on the upper surface of the grid plate and are aligned with the openings associated with control rods 70, 71 yand 72 respectively. It is evident that the guide tubes'serve as a means for guiding the upward movement ofthe control rods to assure that they move along the proper paths. v

As seen in FIG. 3, each of the guide tubes extends upwardly from the grid plate 61 to a vpartition 75. Cables 80, 81 and 82 extends downwardly through openings provided in partition 75 and thence through the guide tubes to the control rods '70, 71 and 72 respectively, holding magnets being disposed at the lower ends of the cables which engage the upper ends, theseholding magnets engaging armatures on the control rods themselves. In the event of a power failure or a danger signal, all magnets are deenergized andallow the control rods to fall into the core. The upper ends of the cables S0, 81 and 82 are connected to winding drums 85, 36 and 87 of Winches 90, 91 and 92 respectively,

the Winches being actuated to control the position of the control rods within the core in accordance with predetermined conditions to maintain the output level of the reactor within desired limits.

Connected in communication withjthe lower portion of the interior of the 'reactor is a first heat exchange conduit supported from the lower wall of housing 45, a second heat exchange conduit 101 also being supported from this lower wal-l. The heat exchange conduits are connected to a circulating pump 103, conduits 10@ and 101 being in communication with opposite sides of the reactor as defined by a relatively thin central partition 105 formed of graphite or the like which divides the reactor into two halves. The guide tubes 70', 71', `and '72 are provided with llateral openings through the side walls thereof such that when pump 103 is operating, coolant fluid will be pumped upwardly vorder to obtain'the desiredeirculation of coolant fluid,

additional openings may be provided in'members 60 and 61. The coolantutilized within the reactor and cham- K' ber 47 may comprise de-mineralized water, the normal level of -the water being indicated by reference numeral 106 and being at the upper portion of chamber 47. A conventional ion exchange lter110 and a circulating e pump 111 are provided for continually treating the coolant iluid as lit passes through chamber 47 in a wellknown manner.

Disposed within chamber 46 is an activated carbon ilter M and a continuously operating fan 116 which circulates the atmosphere within chamber 46 through the lter to continually clarify the atmosphere therein. Fluid pressure conduit 3S extends downwardly through chambers de, 47 and 48 and extends through the lower wall of housing 4S such that fluid under pressure may be pumped downwardly through the conduit to the space beneath the housing. Gas vent conduit Z6 also extends downwardly through chambers 46, 47 and 4S and extends beneath the lower wall of the housinu such that any gas accumulating at this point beneath the housing may be vented at the surface.

As mentioned above, the coolant for the reactor may comprise water, and accordingly, the reactor is designed to operate at approximately the boiling point temperature of water or namely .at C. It will be understood that the thermal output of the reactor must be suitably coupled with the length of the bore hole and the volume of the body of heat-conducting fluid therein. In a typical example wherein the length of bore hole to be heated is 300 feet, the reactor may be operated at a power level of one megawatt. This example assumes a total temperature difference of 80 C. and a thermal conductivity of oil and limestone of about .004. The limitation on the output power of the reactor lies primarily in the ability of the circulating system includo ing the body of heat-conducting fluid and the circulating pump means therefor to transfer the thermal energy from the heat exchanger to the oil-bearing strata and `into the rock above and below the oil-bearing strata.

A bracket l2@ is connected to conduits litt? and lili and extends laterally therefrom. A downwardly extending conduit 124 is clamped to a laterally extending porton of bracket and extends upwardly thereabove to terminate in an upper open end 125. The lower end of conduit 12d is connected to a circulating pump 126 to which a conduit 27 is also connected and is provided with an open upper end. lt is apparent that the open upper ends of conduits 124 and l2? are spaced a considerable distance from one another, conduit 27 serving as an inlet conduit, and conduit l24 serving as an outlet conduit. A bottom plug 12.8 is provided beneath circulating pump En for sealing the bore hole beneath the apparatus. The bottom plug 12S serves to conne the body of heat-conducting uid disposed with the space of the bore hole thereabove. This column of heat-conducting duid may comprise crude oil, water, or other suitable substances as desired, in either case, the lluid being capable of being circulated by the circulating pump 126 along the walls of the bore hole. This column or" fluid extends 'from the bottom plug upwardly to a point immediately below the housing d5 such that the heat exchanger mechanism including conduits i90 and lill is submerged within the column of heat-conducting uid. It will be understood that FIG. 3 is not necessarily proportional and in fact the portion of the bore hole lying between the lower end of housing 45 and the bottom plug 128 may be of a relatively great dimension, and as mentioned previously, this portion of the bore hole may be 300 or more feet in length. Gf course, conduit 124- will be of a suitable length to dispose the circulating pump 126 at the lower portion of the bore hole which is desired to be heated while the upper open end will be disposed adjacent the upper end of the heat exchanger means as shown.

It is apparent that by circulating the body of heat-conducting fluid along the walls of the bore hole and about y the heat exchanger, a very effective heat transfer will be obtained by the heat exchanger to the entire length of the bore hole which is desired to be heated thereby providing as mentioned previously a line source of heat as contrasted to the point source of heat employed with prior art arrangements. In the present example wherein the reactor is operated at a temperature of 100 C., the temperature of the heat conducting fluid along he walls of the bore hole will, of course, be slightly less than 100 C., and the temperature of the heat conducting luid will depend upon the size of the bore hole as well as the volume of the column of heat conducting iluid. Other reactors operating at different temperatures may also be employed, and in such cases, the temperature of the heatconducting iiuid may vary; however, in any case, it is considered that the temperature of the bore hole wall. should not exceed 350 C. since temperatures greater than 350 C. in the oil-bearing strata may result in charring of the oil thereby substantially reducing the efciency of the operation.

While the above description is directed primarily to an arrangement wherein the column of heat conducting fluid is disposed generally only within the oil-bearing strata itself, in many cases, as for example where the strata has a small vertical dimension, it may be desirable, if not necessary, to have the heated column of uid extend above or below or both above and below the oil bearing strata itself.

Referring to FIG. 6, a modification is illustrated wherein corresponding parts have been given the same reference numerals primed. In this instance, it will be seen that the upper end portion 2124i of the circulating system extends above the top layer of cap rock while the inlet portion of the conduit 27 is disposed below the lower layer of cap rock. In this case, the column of heat conducting uid extends a substantial distance both above and below the oil-bearing strata itself as indicated by letter B. The circulating pump means 12d may also be varied in position. It is evident that Whereas the circulating pump is shown as disposed adjacent the bottom plug 12S', it may also be suspended adjacent the heat exchanger mechanism while the conduit 124' will in such instance extend downwardly adjacent to the lower portion of the bore hole.

Referring again to FIG. 2 of the drawing, a rst pressure indicator T is mounted on control panel 2li, this pressure indicator being adapted to indicate the pressure existing beneath the housing 45 by means of a suitable pressure sensing means (not shown). Pump 3l is controlled by switch l/tl which is manually operated. lf the pressure beneath the housing should drop below that which is desired, pump 3l may be energized to supply additional fluid under pressure downwardly through conduit 30. If the fluid pressure in the bore hole should become execs sive, switch 141 may be operated to discontinue operation of como 3l.. Switch is provided for selectively energizing the reactor circulating pump lr03, and switch 43 is employed for selectively controlling the operation of the circulating pump me which controls the circulation of the heat exchange fluid disposed within space 1.30. In-

'icator gauge E45 is connected with a suitable sensing means which indicates the fluid level in space i3@ of the bore hole. If the gas pressure increases excessively, and the tluid level in space 313-0 drops, valve 27 may be actuated to vent the gas beneath the housing l5 through the intermediary of gas vent conduit 26.

in addition, heat conducting lluid may be added to the bore hole through conduit 3l? by means of pump 3l should the level of the fluid in space lid@ drop below the desired position. It is of course essential that the level of the body of uid be maintained so as to submerge the heat exchanger mechanism since the heat conducting fluid must circulate around the beat exchanger to be heated.

Temperature indicators such as indicator T are connected with a thermo-couple 155. which extends within the reactor itself whereby the temperature of the reactor is indicated. indicator l5@ is also connected to an automatic mechanism (not shown) of conventional construction such that the actuation of Winches 9i?, 911. and 92 is automatically controlled in accordance with the temperature existing in the reactor to control the heat of the reactor a-t a predetermined level. This mechanism is adapted to maintain the reactor at a substantially constant temperature and to prevent the development of excess temperatures within the reactor. Other controls necessary to reactor operation are recognized as being part of the present design, but only those controls specific to the operation of the present invention are shown in detail. The actual dimensions of the associated reactor parts are schematic with the intent of making clear various relevant details. In actual construction, the geometry of the various sections would be prescribed by the requirement of obtaining a critical reaction Volume in any appropriate manner.

In carrying out the method of the present invention, the apparatus hereinbefore described is inserted within a central bore hole. The nuclear reactor is then energized to supply heat to the hea-t exchanger mechanism including the conduits 100 and 101. The apparatus then automatically maintains a predetermined temperature in the reactor during operation of the system. body of heat conducting fluid is provided in the space 139 between the heat exchanger and the wall of the bore hole, this fluid preferably being inserted in operative position through conduit 330. The body of heat transferring fluid is then circulated during operation by pump 126 to continuously circulate the fluid around the heat exchanger and along the wall of the bore hole. Fluid pressure may subsequently be provided through conduit 30 to vassist in forcing the oil out of the strata and into one of the surrounding bore holes. The oil is then removed through the bore holes to a suitable reservoir. Itis, of course, understood that the coolant within the reactor and heat exchanger is ordinarily continuously circulated therethrough while the apparatus is in operation. Y

1t is apparent from the foregoing that there is provide a new and novel method and apparatus for recovering oil which can not be recovered by'conventional pumping methods due to the fact that theoil has become excessively viscous and waxy. A nuclear reactor means is pro vided for efficiently producing heat, and means is incorporated for producing a predetermined amount of heat during operation. It should be noted that the source; of heat is disclosed closely adjacent the area Which it is desired to heat, and the circulating heat transfer medium disposed between the heat exchanger and the 'wall of the bore hole effectively provides a line source of heat to there# by provide a maximum degree of eciency in heating the fluid-bearing strata.

In this manner the viscosity of the oil in the jfluid-- bearing strata is decreased by a simple method which may be carried out by even relatively inexperiencedpersonnel. In addition, the apparatus according to the present invention is quite simple and inexpensive in construction, and yet is efficient and reliable inL operation.

As this invention may be embodied in severalY forms without departing from the spirit'or essential charactertive and not restrictive, and since the scope of theinvention is defined by the appended claims, all changes that fall within the metes and bounds of the claims or that form their functional as Well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

We claim:

1.-A method for heating a subterranean petroleumbearing strata having a bore hole extending thereinto comprising providing ay source of heat including heat exchange means in said bore hole, providing a body of heat conductive liquid within said bore hole in contact with said heat exchange means to heat the liquid in Ithe bore hole With the liquid also being disposed adjacent said petroleum-bearing strata and in intimate contact yWith an Yuninterrupted portion of the bore hole wall throughout a substantial length of the bore hole wall adjacent said petroleum-bearing strata and continuously circulating sub- "stantially the entire body of liquid longitudinally of the bore hole between the upper and lower levels of said body of liquid so as to substantially continuously move the liquid along'uninterrupted bore wall portions throughout a substantial length of the bore hole wall and in intimate contact therewith so as to heat a large area of the' bore v hole wall toasubstantially uniform temperature to effectively provide a line source of heat to the adjacent strata.

2. The method as defined in claim l wherein the step of providing a source of heat including heat exchange means in said bore hole comprising supporting a nuclear reactor alongfwith a heat exchanger in said bore hole.

References ACited-by the Examiner UNITED STATES PATENTS 1,147,517l 6/57 France.

OTHER` REFERENCES l TimeMagazine, Mar. 24, 1958, p. 64. Y

CARL D.l QUARFORTH; Primary Examiner. REUBEN EPSTEIN, Examiner-.1' 

1. A METHOD FOR HEATING A SUBTERRANEAN PETROLEUMBEARING STRATA HAV ING A BORE HOLE EXTENDING THERINTO COMPRISING PROVIDING A SOURCE OF HEAT INCLUDING HEAT EXCHANGE MANS IN SAID BORE HOLE, PROVIDING A BODY OF HEAT CONDUCTIVE LIQUID WITHIN SAID BORE HOLE IN CONTACT WITH SAID HEAT EXCHANGE MEANS TO HEAT THE LIQUID IN THE BORE HOLE WITH THE LIQUID ALSO BEING DISPOSED ADJACENT SAID PETROLEUM-BEARING STRATA AND IN INTIMATE CONTACT WITH AN UNINTERRUPTED PORTION OF THE BORE HOLE WALL THROUGHOUT A SUBSTANTIAL LENGTH OF THE BORE HOLE WALL ADJACENT SAID PETROLEUM-BEARING STRATA AND CONTINUOUSLY CIRCULATING SUBSTANTIALLY THE ENTIRE BODY OF LIQUID LONGITUDINALLY OF THE BORE HOLE BETWEEN THE UPPER AND LOWER LEVELS OF SAID BODY OF LIQUID SO AS TO SUBSTANTIALL YDONTINUOUSLY MOVE THE LIQUID ALONG UNINTERRUPTED BORE WALL PORTIONS THROUGHOUT A SUBSTANTIAL LENGTH OF THE BORE HOLE WALL AND IN INTIMATE CONTACT THEREWITH SO AS TO HEAT A LARGE AREA OF THE BORE HOLE WALL TO A SUBSNATIALLY UNIFORM TEMPERATURE TO EFFECTIVELY PROVIDE A LINE SOURCE OF HAT TO THE ADJACENT STRATA. 